Whether driving across town to meet a friend, or driving across country to meet a relative, drivers often like to provide the person they're meeting with an estimated time of arrival. This helps the person being met plan their schedule accordingly, so they can ensure that they're present when the traveler arrives.
Unfortunately, due to weather, road repair, traffic, detours, unplanned stops, etc., travelers are often delayed, and many times they may not arrive anywhere near the estimated arrival time. While the frequency of cellular phones has made it easier to call and update an estimated arrival time, a driver may often not think to do this at each point of delay, or their phone may have died, or there may be a myriad of other reasons why they cannot or do not update their arrival time.
Additionally, emergencies or other reasons may arise why a person being met needs to briefly leave the house. Of course, unless they know with reasonable certainty that their guest is not expected to arrive while they're gone, they may not leave the house in these circumstances, lest their guest be stuck waiting for them to return upon the guest's arrival.
Numerous cars come equipped with GPS systems or other navigation systems, that allow the vehicle to know where it is geographically located. Additionally, vehicles may even have cameras on-board that allow the vehicle to take a photograph of its present location.